Make sensor data available for (custom) live tracking
External (and internal) sensor data, especially heart rate, but also other BLE / ANT+ sensor data like pedal frequency for bikers, is already available for track recording.
I would like to suggest to create custom live tracking parameters for all that sensor data or at least heart rate, too. Then it would be possible to send those live to a custom tracking server.
It would be even worth thinking about additional internal sensor data (like orientation from an internal gyroscope / magnetic compass or data from an internal temperature sensor). If available in the mobile device, it would be really nice to be able to both record them in a track and send them to a server via live tracking.